Glossary of elastomer processing
EMC gaskets (EMC/EMI shielding gaskets)
EMC gaskets are conductive gaskets that attenuate electromagnetic interference (EMI) at gaps, covers and connection points of enclosures and, depending on the design, also seal against environmental influences (dust/moisture). They close gaps, create electrical contact between enclosure parts and increase the shielding effectiveness of the entire assembly.
Synonyms and distinction
- EMC gasket = general term; German: EMV-Dichtung (EMV = elektromagnetische Verträglichkeit)
- EMI gasket (component function) vs. EMC (system goal “electromagnetic compatibility”)
- Not a substitute for EMC measures on the circuit board (layout/filters), but complementary enclosure shielding
Typical applications
- Enclosure covers, seals in control cabinets, connector environments
- Electronic assemblies and components, laboratory/medical devices, controllers, telecoms/5G
- Vehicle electronics, battery/inverter housings, rail/aerospace modules
Material classes and properties
| Material | Structure | Key data | Use | Notes |
|---|---|---|---|---|
| Conductive elastomers (silicone, FKM, EPDM) with fillers | Matrix + conductive particles (e.g. silver-aluminium, silver-copper, nickel-graphite) | Low surface/volume resistance, SE* up to approx. 80 to 100 dB (frequency-dependent) | Enclosure joints with IP requirement, large compression travel | Consider galvanic compatibility and corrosion protection |
| Fabric over foam | Conductive fabric laminated onto PU/PE foam | Very good SE at low closure forces, cost-efficient | Electronics front panels, EMC gasket + comfortable compression | Not for aggressive media/high IP without additional sealing |
| Knitted wire mesh / wire gaskets | Monel, stainless steel, tin-plated copper etc., also as hybrid (metal + elastomer) | High SE into the GHz range, temperature-stable | Control cabinet doors, RF sealing strips, shelter doors | Mechanically more robust, needs even contact |
*SE = shielding effectiveness, typically given in dB over the frequency range.
Key figures and selection criteria
- Shielding effectiveness (dB) over frequency (e.g. 30 MHz to 6 GHz); note the measuring method
- Contact resistance and specific resistance (surface/volume)
- Compression (typically 10 to 30 % for elastomer gaskets) and compression set
- IP protection (combination of EMC + environmental sealing), UV/temperature/chemicals
- Galvanic pairing (e.g. Ag-coated fillers on aluminium: avoid corrosion)
Test methods and standards (selection)
- ASTM D4935: shielding effectiveness of planar materials (coaxial method)
- IEEE 299 (formerly MIL-STD-285): shielding effectiveness of complete enclosures/shelters
- IEC/EN 61000-5-7: evaluation of the shielding of empty enclosures, marking code
- MIL-DTL-83528: requirement specification for conductive elastomer gaskets
These standards address material tests vs. system tests; the choice depends on the component, frequency and acceptance criteria.
Design and installation: best practices
- Ensure a continuous conductive path along the gasket
- Even closure forces; take screw spacing and frame stiffness into account
- Clean conductive contact surfaces (coating), avoid oxidation
- Use the adhesive layer only as an installation aid, not as the sole contact
- For IP requirements, use a double seal (EMC + environmental) or hybrid profiles
FAQ: EMC gaskets
How can I tell how well a gasket performs?
By the shielding effectiveness in dB over frequency (e.g. ASTM D4935 curve) and by the contact resistance.
Is a material test sufficient?
For component acceptance, a system test (e.g. IEEE 299/IEC 61000-5-7) is often advisable. Material values alone are not the same as enclosure SE.
Are there corrosive pairings?
Yes. For example, silver-containing fillers on bare aluminium can promote galvanic effects. Choose corrosion protection and a suitable material pairing.
Questions about this term?
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